[SQL] NodeJs connects to MySql and MySql common statements

1. Install mysql

npm install mysql

2.Get MySql

import mysql from 'mysql'

3. Connect to MySql

const connection = mysql.createConnection({
  host: 'yourServerip',
  user: 'yourUsername',
  password: 'yourPassword',
  database: 'yourDatabase'
})

connection.connect(err => {
  if (err) {
    console.error('数据库连接失败: ' + err.stack)
    return
  }
  console.log('数据库连接成功', err)
})

Execute Mysql addition, deletion, modification and query

const sqlSentence = 'yourSqlStatementOrAddOrDeleteOrPutOrSelect'

connection.query(sqlSentence , (error, results, fields) => {
  if (error) {
    console.error('失败: ' + error)
    return
  }
  console.log('成功:',results)
})

MySql addition, deletion, modification and query common statements

Inquire

select * from table name; //Query all data in the table
​
select * from table name 1 union select * from table name 2 union select * from table name 3; //Query all data in multiple tables
​
select * from table name where id = 4; //Query a single row of data in the table

Increase

1. Add column value
insert into table name (column name) values ​​(column value); //Add column value

insert into table name (column name 1, column name 2, column name 3, column name 3) values ​​(column value 1, "column value 2", column value 3, "column value 4"); //Add more column values

2. Add column name
alter table table name add column name type //add column name

Revise

1. Modify column values
update table name set column name 1 = "column value 1" where id = 4; //Modify a single
​
update table name set column name 1 = "column value 1", column name 2 = "column value 2" , column name 3 = "column value 3" where id = 4; //Modify multiple
​
2. Modify column names
alter table table name change old column name new column name new type;
​
alter table table name change old column name 1 new column name 1 new type 1, change old column name 2 new column name 2 new type 2; //Modify multiple column names

delete

1. Delete column values
delete from table name; //Delete all values ​​in the table
​
delete from table name 1, table name 2, table name 3; //Delete all values ​​in multiple tables
​
delete from table name where id = 5; //Delete a single row value in the table
​
2. Delete column names
alter table table name drop column column name;
​
alter table table name drop column column name 1, alter table table name drop column column name 2; //Delete multiple column names
​
3. Delete column names and values
truncate table table name //Delete all column names and column values ​​in the table